Bomb fuse



wt. E5, 1946.. R, L.. GRAUMANN BOMB FUSE Filed Marh 2, 1932 2Sheets-Sheet 2 l-wepor:

Granma l 53, d, azrrzeg Patented Cct. 15, 1946 BOMB FUSE Raymond L.Graumann, Alexandria, Va.

Application March 2, 1932, Serial No. 596,364

7 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757

This invention relates to bomb fuses, and more particularly to fuses forbombs launched from aircraft in which the fuse is armed by the action ofthe air on a propeller.

The objects of this invention are, first, to provide a fuse that hassufcient delay action that it will not arm until after it is clear ofthe airplane;

Second, to provide a fuse that has instantaneous action on impact;

Third, to provide a fuse that will automatically disarm at apredetermined reduced air speed;

Fourth, to provide a fuse that, after arming, so locks the armingmechanism that after disarming at a reduced air speed, it cannot bere-armed;

Fifth, to provide a fuse that is easily removed from the bomb and issafe during shipping; and

Sixth, to provide a fuse that is safe from accidental firing.

With the above and other objects in view, this invention consists ofsuch construction and arrangement of parts as will be more fullydescribed hereinafter in connection with the accompanying drawings, inwhich:

Fig. 1 shows the fuse in the unarmed condition;

Fig. 2 is a cross-section of the fuse on line 2--2 of Fig, l;

Fig. 3 is a cross-section of the fuse on line 3-3 of Fig. l;

Fig?. 4 is a cross-section of the fuse on line l-ll of Fig. 1;

Fig. 5 shows the fuse in the armed condition;

Fig. 6 is a crosssection of the fuse on line 6-6 of Fig. 5;

Fig. 7 is a cross-section of a part of the fuse on line l-l of Fig. 2;

Fig. 8 is a view of the arming nut; Fig. 9 shows the arming nut guide;

Fig. l shows the detonator holder.

The Cotter pin I-I insures the safety of the bomb during shipping and isremoved when the bomb is placed in the racks on the airplane. The armlngwire I2 is secured to the airplane and is pulled out of the fuse by theweight of the bomb as it is released. Once the bomb is launched, the airact--l ing on propeller I3 turns shaft VIll until stop pin I strikesstop pin I5. As the velocity of the bomb through the air increases, thepressure on the propeller and hub overcomes the spring Il, forcing theshaft IA and arming nut I8 inward until the guide pins I9 reach thebottom of the slots 42, Fig. 9, in arming nut guide 20. The ball race2l, due to securing pin 22 and collar 23, is carried inward with theshaft at the same time, which m0- tion is suioient to cause stop pin I5to clear stop pin IS so that the propeller and shaft may again turn. Theshaft will advance relative to the fuse body until shear pin collar 24rests against the top of housing 25. Thereafter, the arming nut I8 willmove outward relative to the fuse body. Resistance to turning of theshaft is small, due to the ball race 12| which has a stationary partresting against spring I'I and a moving part pinned to the shaft withthe balls in between. If at any time the pressure on the propeller andhub is reduced below that required to compress the spring Il, the shaftwill be forced outward so that the stop pins l5 and I6 again strike andfurther rotation is prevented. However, during the continued rotation ofthe shaft, arming nut I8 advarices until it strikes collar 23, whenguide pins 'I9 are clear of the slots in the arming nut guide 2li, andthe firing pin 28 is clear of the arming nut, but rotor arming pin 2'6carried outward by nut it is still projecting slightly into detonatorrotor .il,Fig. 6, and further rotation of the shaft carries the armingnut with it and they move until guide pins I9 rest against the shoulderson the top of the arming nut guide, Fig. 5. In this position the guidepins are above slots 29 which permit suiiicient movement of the armingnut to fire the fuse. During the turning of the arming nut after pins I9have moved clear of slots 42, rotor arming pin 2S carries the detonatorrotor around an equal amount. The point of the firing pin 28 is then atthe other end of groove 30, Fig. 3, directly over` detonator 3i, Fig. 5.The detonator and lead 32 to booster charge 33 are then in line andready for firing. Arming nut lock pin 34, Figs. 2 and '7, is so locatedthat during the rotation of the arming nut it passes over the bottom ofslot 29 without engaging it, but engages elongated opening 35 when thearmed position has been reached, as in Fig. 5. This elongated openingmust allow sutilcient inward movement of the arming nut to eX- plode thefuse, and suicient outward movement to disarm it. Upon impact, thearming vane, hub, shaft and nut are driven rearward, shearing the pin 36and the thin flange 43 on the firing pin` driving the firing pin intothe detonator which through the lead and booster charge detonates thebomb.

In case the fuse is accidentally armed while the carrying airplane isdiving at high speed, and is not dropped, a safety feature is providedto unarm the fuse before the airplane lands. It comprises a spring 31,one end of which is anchored in the arming nut guide and the other inthe detonator rotor. This spring is slightly wound about itslongitudinal axis in the unarmed prevents the rotation of the otherparts, the Y fuse cannot be re-armed without being disassem;

bled.

fuse may be removed from the bomb. The-'arming nut guide is preventedfrom turning'in the fuse body by dowel pin 39. It isfurther secured inthe fuse body by the housing 25 which nts against it and is held in4 thefuse body by locking screw 4B.

f A delay in the arming of the fuse is provided to insure its clearingthe airplane before it arms. This is accomplished by the small pressureangle on the propeller blades in combination with the ne pitch of thescrew threads in the arming nut.

The locking nut assures an explosion on impact by holding the fuse inthe proper armed position.

`The detonatorbeing out of line in the unarmed position makes the fusesafe in shipping, and prevents accidental firing of the bomb.

It will be understood that the above description and accompanyingdrawings comprehend only the general' and preferred embodiment of myinvention, and that minor changes in the details of construction andarrangement of parts may be made within the scope of the appended claimswithoutrsacricing any of the advantages of this invention.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

I claim:

f l, A bomb fuse comprising a fuse body having a'cavity therein, adetonator holder, an arming nut, an arming nut guide, a fuse bodyhousing, a shaft Vpenetrating said fuse having screw threads on theinner-end, said screw lthreads being engaged by said arming nut, saidarming nut guide preventing rotation of said arming nut until after a;predetermined number of revolutions of said shaft, a propeller and hubattached to said shaft, a rst spring located in said fuse body, meansassociated with said shaft whereby said shaft and propeller areprevented from rotating until the longitudinal force exerted by the airon said propeller and hub is sufficient to overcome said' first spring,a firing pin, a detonator, a lead to an explosive charge, the latterthree elements being out of line when the fuse is unarmed and being inline when the fuse is armed, a second spring associated with saiddetonator holder, means associated with said arming nut to move saiddetonator holder'to the armed position, said means and second springoperating to return said detonator from the armed to the unarmedposition when the longitudinal force exerted by the The fuse body sa isthreaded in order that die 4 air on said propeller and hub ceases to besufcient to overcome said rst spring.

2. A bomb fuse comprising a fuse body having a cavity therein, a ringpin mounted in said cavity, an arming nut housing a portion of saidfiring pin in the unarmed position, a threaded shaft engaged by saidarming nut to translate said nut and unhouse said ring pin, an armingnut guide which prevents rotation of the arming nut until said firingpin has been completely unhoused, a detonator rotor having in it adetonator out of line with said firing pin in unarmed position,.andmeansconnecting said rotor to said nut whereby rotation of said nut movessaid detonator into line with said firing pin.

3. A bomb fuse comprising a firing pin, a detonator holder, a detonatorout of line with said ring pin in the unarmed position, a propeller`vand shaft for moving said detonator holder to the armed position, andmeans for returning said detona'tor holder to the unarmed position whenthe longitudinal force exerted by the air on said propeller is reducedbelow a predetermined amount.

4. A bomb fuse comprising a threaded shaft, an arming nut engaging saidshaft, and an arming nut guide for preventing said arming nut fromturning until after a predetermined number of revolutions of said shaft,and thereafter permitting turning of said arming nut through apredetermined ang'le to the armed position, said guide permittingsuiicient longitudinal movement of said arming nut in the armed positionto explode said fuse.

5. VA bomb fuse comprising a shaft having a threaded portion, an armingnut engaging said shaft, an arming nut guide preventing the turning ofsaid nut until after a 'predetermined number of revolutions of saidshaft, and thereafter restricting its turning to a predetermined angleto the armed position, and means for locking said nut in the armedposition. y

6. A bomb fuse comprising a fuse body, a spring located in said fusebody, a shaft penetrat-Y ing said fuse body, a ball race having a nrstpart secured to said shaft and a second part held in position by acollar on said shaft, said spring pressing against said second part, ai'lrst stop pin in said fuse body, and a second stop pin vin said firstpart engaging said rst stop pin uutilsaid shaft and ball race are forcedinto said fuse body against said spring pressure a predetermineddistance.

'7. A bomb fuse, comprising a rotatably mounted shaft, a propeller onsaid shaft,- means initially preventing rotation of said shaft` througha complete revolution, yieldable means acting upon said shaft, saidshaft being longitudinally movable against said yieldable means by airpressure above a predetermined magnitude to render the first said meansineffective to prevent rotation of said shaft, amember rotatable by saidshaft from aninitialposition to a second position to arm the fuse, andmeans to move said mem-n loer to the unarmed position when the torqueex-` erted by said shaft'becomes less than a predetermined minimumbefore impact of the bomb upon an object. l

RAYJIOND L. GRAUMANN.V

